feat(backup): take Tinyforge DB snapshot before every deploy

Adds an opt-in "auto_backup_before_deploy" setting that triggers a
"pre-deploy" backup at the start of every project deploy via the deploy
pipeline (covers both the async HTTP path and the sync poller/webhook
path). Failures are logged to the deploy log but do not abort — missing
a backup is preferable to refusing to ship a fix.

- store: settings.auto_backup_before_deploy column + scan/update wiring
- backup: accept "pre-deploy" as a valid backup_type
- deployer: small PreDeployBackuper interface, hooked into runDeploy
  right after settings load and before any state-mutating work
- api: settings request/response surface the new flag
- web: ToggleSwitch on the backup settings page; "Pre-deploy" badge
  variant in the backup list (badge-warning so it stands out)
- i18n: en/ru strings for the toggle, help text, and badge label

internal/backup/engine.go

@@ -42,7 +42,7 @@ func (e *Engine) BackupDir() string {
 func (e *Engine) CreateBackup(backupType string) (store.Backup, error) {
 	// Validate backup type to prevent path traversal via filename.
 	switch backupType {
-	case "manual", "auto", "pre-restore":
+	case "manual", "auto", "pre-restore", "pre-deploy":
 		// valid
 	default:
 		return store.Backup{}, fmt.Errorf("invalid backup type: %q", backupType)